What are the errors in this presentation . . . seems logical and well thought out . . . the failure of the original floors would not logically be all at once but could be gradual or very uneven based on uneven heat transference . . . and then the average resistance force of the remaining building . . . ??? With 8.62 meters per second downward force of the mass of the 15 floors in the North Tower and assuming zero resistance of the missing floor that was removed by fire and crash damage . . . it should have taken at least 44 seconds to crush the building to the ground . . . is he wrong? If so WHY?

What are the errors in this presentation . . . seems logical and well thought out . . . the failure of the original floors would not logically be all at once but could be gradual or very uneven based on uneven heat transference . . . and then the average resistance force of the remaining building . . . ??? With 8.62 meters per second downward force of the mass of the 15 floors in the North Tower and assuming zero resistance of the missing floor that was removed by fire and crash damage . . . it should have taken at least 44 seconds to crush the building to the ground . . . is he wrong? If so WHY?

I've not gone over it in detail, and not seen how he calculated the upwards force, but gravity (the downwards force) is a constant acceleration, so it's speeding up the block the whole time. The upwards retarding force is a mostly instantaneous force during the impact with a floor. So it is is only slowing the upper block down for the period of impact. Hence the effect of gravity is vastly greater than the effect of the upwards resistance.

This calculation is much easier understood in terms of energy. There's the energy in the falling block, which rapidly increases as it falls - both from gravity and from increase in mass, as more of the building is falling.. Then there's the energy required to break the floor-column connections so the fall can continue.

I'm off to superbowl in in a bit, but I'd like to revisit this at some point, as dealing with actual numbers should be a very level playing field.

The upwards retarding force is a mostly instantaneous force during the impact with a floor . . .

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Are you saying he did not account for the instantaneous nature of the collisions and the acceleration of the combined mass of the successive crumpling building plus the first 15 floors . . . I thought he addressed that . . . I could be mistaken . . .

What are the errors in this presentation . . . seems logical and well thought out . . . the failure of the original floors would not logically be all at once but could be gradual or very uneven based on uneven heat transference . . . and then the average resistance force of the remaining building . . . ??? With 8.62 meters per second downward force of the mass of the 15 floors in the North Tower and assuming zero resistance of the missing floor that was removed by fire and crash damage . . . it should have taken at least 44 seconds to crush the building to the ground . . . is he wrong? If so WHY?

1) Miscalculation of the tonnage of the building. Subject quotes, 68,000 tonnes for top 15 floors. 110/15=7.33

So the total weight of the building, according to subject is, 7.33x68,000=496,400 tonnes. That's too much. The concrete (per tower) is close to 100,000 tonnes (plus/minus 10k - more likely +), steel the same figure. So we're really looking at 220,000 tonnes plus furniture. That's not too easy to estimate - but it's going to be in the thousands of tonnes - you try to work it out - how much does a work station, desk, screen, curtain, carpet, weigh exactly? And how many were on each floor of the tower in question? I'd be inclined to add 60,000 tonnes, which represents just over 500 tonnes per floor. Total weight of building at 280,000 tonnes is more accurate. So subject needs to adapt numbers in his sums.

2) The second error stems from the first - and it's the mass calculation which is wrong. The result of that would be to slow down the rate of acceleration a little.

3) No consideration is made for the fact that the structural aspect of the tower becomes more robust as the 'collapse' progresses. ie. more resistance the further down you go, as the lower parts of the tower are made from thicker steel, etc. eg. The vertical steels at the base of the towers were 5inches thick, 4.5foot longx2foot wide box welded columns with 3.5inch welded bracing internally. That's a beast of a thing - specially when it's tied to 46 just the same via diagonal and horizontal bracing. A beast.

The calculations suffer from the same inaccuracies as my own on the reduction of steel rc to 60 micron dust. But you have to start somewhere. And the subject did. And it's important to say that the subject's calculations are exactly right, there's no problem with the maths at all. That may well be my most important point - on behalf of the subject. I feel like a bit of a bitch for pointing out the errors, but at the end of the day, they don't make a big difference to the point, even though I admit it mysef after all these words of mine. And the point is - the given explanation doesn't add up - if it did, we wouldn't be here.

1) Miscalculation of the tonnage of the building. Subject quotes, 68,000 tonnes for top 15 floors. 110/15=7.33

So the total weight of the building, according to subject is, 7.33x68,000=496,400 tonnes. That's too much. The concrete (per tower) is close to 100,000 tonnes (plus/minus 10k - more likely +), steel the same figure. So we're really looking at 220,000 tonnes plus furniture. That's not too easy to estimate - but it's going to be in the thousands of tonnes - you try to work it out - how much does a work station, desk, screen, curtain, carpet, weigh exactly? And how many were on each floor of the tower in question? I'd be inclined to add 60,000 tonnes, which represents just over 500 tonnes per floor. Total weight of building at 280,000 tonnes is more accurate. So subject needs to adapt numbers in his sums.

2) The second error stems from the first - and it's the mass calculation which is wrong. The result of that would be to slow down the rate of acceleration a little.

3) No consideration is made for the fact that the structural aspect of the tower becomes more robust as the 'collapse' progresses. ie. more resistance the further down you go, as the lower parts of the tower are made from thicker steel, etc. eg. The vertical steels at the base of the towers were 5inches thick, 4.5foot longx2foot wide box welded columns with 3.5inch welded bracing internally. That's a beast of a thing - specially when it's tied to 46 just the same via diagonal and horizontal bracing. A beast.

The calculations suffer from the same inaccuracies as my own on the reduction of steel rc to 60 micron dust. But you have to start somewhere. And the subject did. And it's important to say that the subject's calculations are exactly right, there's no problem with the maths at all. That may well be my most important point - on behalf of the subject. I feel like a bit of a bitch for pointing out the errors, but at the end of the day, they don't make a big difference to the point, even though I admit it mysef after all these words of mine. And the point is - the given explanation doesn't add up - if it did, we wouldn't be here.

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So Lee . . . you agree the (unless you have a better name) Crush Rate would exceed 44 seconds??

So you would consider this to be conclusive proof of controlled demolition then?

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If I may . . . it is potential evidence that what we thought we witnessed in approximately 10 seconds is not explainable by rudimentary physics as was presented by the presenter in the YouTube and a quick analysis by Lee . . .

So you would consider this to be conclusive proof of controlled demolition then?

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It is the position of the presenter that the fall rate could only be justified if the foundation of the buildings were somehow compromised . . . otherwise the upward resistance of the intact 95 floors would prevent such increased acceleration . . . at least at the rate observed. . .

It is the position of the presenter that the fall rate could only be justified if the foundation of the buildings were somehow compromised . . . otherwise the upward resistance of the intact 95 floors would prevent such increased acceleration . . . at least at the rate observed. . .

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That does not make any sense. If the foundation were compromised, then the entire building would fall as one. The bottom of the building never moved until the collapse wave reached it.

That does not make any sense. If the foundation were compromised, then the entire building would fall as one. The bottom of the building never moved until the collapse wave reached it.

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Compromised does not mean complete failure . . . just providing less resistance to the downward force of the building above . . . I am just reporting what the presenter suggests . . .

As I calculate it, accounting for the terminal velocity of around 90/m/s/s or an average velocity of 45/m/s/s, the building could have fallen 450 meters or 1,476 feet in 10 seconds but fell instead 361 meters or 1,184 meters or 36/m/s/s which is about 80% of a free fall rate at sea level . . . without air resistance the distance would have been 490 meters or 1,568 feet in 10 seconds . . . based on d=(0.5 x 9.8 m/s/s) x (Time Sq or 100) . . .

Conclusion: The bottom 95 floors offered a measurable amount of resistance to the fall of the North Tower . . . it slowed the descent of the top part of the building about 20%.

Question: Is this less resistance or more than would have been expected?

Compromised does not mean complete failure . . . just providing less resistance to the downward force of the building above . . . I am just reporting what the presenter suggests . . .

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Actually, that's not what he suggests. He says that the top-down collapse of the building is an indication that the foundation was not damaged (in the first video)

As I calculate it, accounting for the terminal velocity of around 90/m/s/s or an average velocity of 45/m/s/s, the building could have fallen 450 meters or 1,476 feet in 10 seconds but fell instead 361 meters or 1,184 meters which is about 80% of a free fall rate at sea level . . . without air resistance the distance would have been 490 meters or 1,568 feet in 10 seconds . . . based on d=(0.5 x 9.8 m/s/s) x (Time Sq or 100) . . .

Conclusion: The bottom 95 floors offered a measurable amount of resistance to the fall of the North Tower . . . it slowed the descent of the top part of the building about 20%.

Question: Is this less resistance or more than would have been expected?

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Well, according to your video, it's vastly less. However he's making the fundamental error that the upwards force is equal to the downward force. Basically saying that upon impacting a floor, the upper block will stop entirely. That is total nonsense.

You have to look at the basic mechanisms of failure. There's basically horizontal structures (the floors) and vertical structures (the columns). Now the columns can carry a lot of weight, so long as they are both vertical, and braced at regular intervals. The floors cannot carry much weight. So if you drop a large mass on the floor, it will fail. This both removes the bracing, and pushes and pull the vertical columns so they will fail. The outside columns will fall away from the building as their lose floors, the interior columns will fail similarly inside the building, but more needs to be stripped away before they fail.

But these things don't happen at the same time for the same floor. Vertical structures would likely collapse only after several floors worth of horizontal structures have been stripped away. And they would require relatively small amounts of energy to collapse - in fact the exterior columns would have buckled and collapsed simply under their own weight, with no additional force needed.

So it's a bit more complex than his simple equations. You don't have a solid block falling onto another solid block. The initial floor-floor impact would compact the bottom floor of the top block as much as the top floor of the bottom block. But after that you've essentially got a falling mass of compacted floors that grows rapidly, getting bigger and bigger, doing more damage to the lower floor than the upper floors. Each floor detached adds to the falling block. The retarding energy acting on the top of the top block is approximately the energy required to break the horizontal members away from the vertical members, plus a small amount required to push the vertical members.

This is an old argument. The truther versions of it range from simple incredulity to calculations to rely on incorrect assumptions (like in your linked video), to calculations that simply plug in excessively large amounts of energy required to "destroy" each floor, rather than simply separate it, loading to collapse with buckling.

It's difficult to debunk this subject, because it's complicated, but one authoritative anaysis of the subject is:

Mechanics of Progressive Collapse: Learning from World
Trade Center and Building Demolitions

The kinetic energy of the top part of the tower impacting the
floor below was found to be about 8.4 larger than the plastic
energy absorption capability of the underlying story, and considerably
higher than that if fracturing were taken into account
Bažant and Zhou 2002a. This fact, along with the fact that
during the progressive collapse of underlying stories Figs. 1d
and 2 the loss of gravitational potential per story is much greater
than the energy dissipated per story, was sufficient for Bažant and
Zhou 2002a to conclude, purely on energy grounds, that the
tower was doomed once the top part of the tower dropped through
the height of one story or even 0.5 m. It was also observed that
this conclusion made any calculations of the dynamics of progressive
collapse after the first single-story drop of upper part superfluous.The relative smallness of energy absorption capability
compared to the kinetic energy also sufficed to explain, without
any further calculations, why the collapse duration could not have
been much longer say, twice as long or more than the duration
of a free fall from the tower top.

Abstract: Previous analysis of progressive collapse showed that gravity alone suffices to explain
the overall collapse of the World Trade Center (WTC) towers. However, it remains to be checked
whether the recent allegations of controlled demolition have any scientific merit. The present analysis
proves that they do not. The video record available for the first few seconds of collapse is shown to
agree with the motion history calculated from the differential equation of progressive collapse but,
despite uncertain values of some parameters, it is totally out of range of the free fall hypothesis, on
which these allegations rest. It is shown that the observed size range (0.01 mm—0.1 mm) of the
dust particles of pulverized concrete is consistent with the theory of comminution caused by impact,
and that less than 10% of the total gravitational energy, converted to kinetic energy, sufficed to
produce this dust (whereas more than 150 tons of TNT per tower would have to be installed, into
many small holes drilled into concrete, to produce the same pulverization). The air ejected from the
building by gravitational collapse must have attained, near the ground, the speed of almost 500 mph
(or 223 m/s, or 803 km/h) on the average, and fluctuations must have reached the speed of sound.
This explains the loud booms and wide spreading of pulverized concrete and other fragments, and
shows that the lower margin of the dust cloud could not have coincided with the crushing front. The
resisting upward forces due to pulverization and to ejection of air, dust and solid fragments, neglected
in previous studies, are found to be indeed negligible during the first few seconds of collapse but not
insignificant near the end of crush-down. The calculated crush-down duration is found to match a
logical interpretation of seismic record, while the free fall duration grossly disagrees with this record.

However he's making the fundamental error that the upwards force is equal to the downward force. Basically saying that upon impacting a floor, the upper block will stop entirely. That is total nonsense.

You have to look at the basic mechanisms of failure. There's basically horizontal structures (the floors) and vertical structures (the columns). Now the columns can carry a lot of weight, so long as they are both vertical, and braced at regular intervals. The floors cannot carry much weight. So if you drop a large mass on the floor, it will fail. This both removes the bracing, and pushes and pull the vertical columns so they will fail. The outside columns will fall away from the building as their lose floors, the interior columns will fail similarly inside the building, but more needs to be stripped away before they fail.

But these things don't happen at the same time for the same floor. Vertical structures would likely collapse only after several floors worth of horizontal structures have been stripped away. And they would require relatively small amounts of energy to collapse - in fact the exterior columns would have buckled and collapsed simply under their own weight, with no additional force needed.

So it's a bit more complex than his simple equations. You don't have a solid block falling onto another solid block. The initial floor-floor impact would compact the bottom floor of the top block as much as the top floor of the bottom block. But after that you've essentially got a falling mass of compacted floors that grows rapidly, getting bigger and bigger, doing more damage to the lower floor than the upper floors. Each floor detached adds to the falling block. The retarding energy acting on the top of the top block is approximately the energy required to break the horizontal members away from the vertical members, plus a small amount required to push the vertical members.

This is an old argument. The truther versions of it range from simple incredulity to calculations to rely on incorrect assumptions (like in your linked video), to calculations that simply plug in excessively large amounts of energy required to "destroy" each floor, rather than simply separate it, loading to collapse with buckling.

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Fantasy. These contortions are equal to the 'building within a building' stuff. The guy made an effort to actually do the maths - and the maths is right, no matter your protestations, if not a perfect representation. He doesn't claim perfection. But basically it's correct - and you know it. Don't you? How long should the building have taken to reach the ground? - let's see your maths in his terms and based on my calculation of the total weight of one tower which is 280,000 tonnes including furniture. If what we're told is true, then how long for 'The Crusher' (ie. the top 15 floors - which actually weighed about 38,000 tonnes) to hit the ground after crushing the building and then itself, leaving nothing recognizable as a building, and likewise its contents (yes, that's the story, I feel sullied just repeating it). Can we see that from you in the terms I propose?

It is the position of the presenter that the fall rate could only be justified if the foundation of the buildings were somehow compromised . . . otherwise the upward resistance of the intact 95 floors would prevent such increased acceleration . . . at least at the rate observed. . .

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And he is right to say that. And to corroborate, there are scores, if not hundreds, of eyewitness accounts of explosions and destruction in the lower levels (lobbies and below) of the buildings. That's a direct connection in evidence.

Fantasy. These contortions are equal to the 'building within a building' stuff. The guy made an effort to actually do the maths - and the maths is right, no matter your protestations, if not a perfect representation. He doesn't claim perfection. But basically it's correct - and you know it. Don't you? How long should the building have taken to reach the ground? - let's see your maths in his terms and based on my calculation of the total weight of one tower which is 280,000 tonnes including furniture. If what we're told is true, then how long for 'The Crusher' (ie. the top 15 floors - which actually weighed about 38,000 tonnes) to hit the ground after crushing the building and then itself, leaving nothing recognizable as a building, and likewise its contents (yes, that's the story, I feel sullied just repeating it). Can we see that from you in the terms I propose?

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The mass of the building makes no difference to his calculations. He says that when the falling block is in contact with the building, then the building exerts an upwards force equal to the downwards force. This is correct. It's like if you place one brick on top of a pile of nine bricks, it's in equilibrium, the forces are balanced.

He then says that the upped block exerts a downwards force of ma (mass times acceleration, really should be mg, but it's the same thing). He then says the lower block exerts (or rather is capable of exerting, otherwise he's saying the top of the building should float away) an upwards force of (ma + the mass of the people + some safety factor). This is also true. The lower block is normally capable of supporting the weight building above it plus quite a bit extra. The bottom floors are capable of supporting the entire weight of the building, plus more. In fact, if his logic was correct, the upper block would slow down and stop after just a few floors.

Where he is wrong is in describing this upwards force as a constant force. It's not. gravity is a constant force, accelerating downwards. The upwards force only happens DURING CONTACT. When the upper block fall onto the lower block, there's a collision, the floor fails, and the block continues to accelerate.

So the upwards force will only affect the acceleration WHILE THE FLOOR IS BEING DETACHED. i.e., only while the joints are failing. That failure only takes a fraction of a second. But to calculate the amount of upwards force under his assumptions, you'd need to know how long it takes the floor to fail when 38,000 tonnes are dropped on it.

And he is right to say that. And to corroborate, there are scores, if not hundreds, of eyewitness accounts of explosions and destruction in the lower levels (lobbies and below) of the buildings. That's a direct connection in evidence.

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Explain how weakening the foundation would make the block fall faster. Are you suggesting that the core columns were disintegrating inside the building from the bottom up?

So the upwards force will only affect the acceleration WHILE THE FLOOR IS BEING DETACHED. i.e., only while the joints are failing. That failure only takes a fraction of a second. But to calculate the amount of upwards force under his assumptions, you'd need to know how long it takes the floor to fail when 38,000 tonnes are dropped on it.

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So Mick how much of a fraction of a second does it take . . . how much time are you talking about . . . 95 of them? That would add up rather quickly don't you think?

So Mick how much of a fraction of a second does it take . . . how much time are you talking about . . . 95 of them? That would add up rather quickly don't you think?

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The point is that most of the time the building is not slowing down. The MOST it could take, as a proportion of the total time would be the ratio between the thickness of the floor, the the height between the floor and the ceiling. Or about the 20% you mentioned.

Of course that's all a gross simplification - his reasoning is fundamentally flawed.

"When Flight 11 hit, he had been standing in front of a Banana Republic store in the enclosed shopping mall and concourse beneath the two towers, a spot he occupied four mornings a week and where thousands of people exiting the subways could see him. Whitaker had been stunned by a fireball that ran down an elevator shaft in the north tower."

Content from external source

Kenny Johannemann was in the number one tower of the World Trade centre, waiting for the elevator in the basement. It was shift-change time, the time of day when the building is most crowded.

"The lift door exploded open. there was a man inside half burnt. His skin was hanging off."

Vertical structures would likely collapse only after several floors worth of horizontal structures have been stripped away. And they would require relatively small amounts of energy to collapse - in fact the exterior columns would have buckled and collapsed simply under their own weight, with no additional force needed.

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NONE of the vertical columns, whether internal or external, were capable of stably supporting their own weight. The whole structure relied on the cross-bracing of the floors, and particularly the top hat truss and the engineering floors, for stability. Without that those columns were spaghetti. Even if the column sections were 5" thick at the foundations.

No, he says if the foundation is broken then the lower part of the building will fall. See 2:25 "however, what we saw was the opposite, we saw a collapse beginning from the top and going down"

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I know Mick . . . that is the point . . . to explain such a swift failure of the entire building . . . it would normally require the bottom to fail to allow the building above the foundation to fall apart supplying minimal resistance to the upper floors to fail and fall in the time we observed. And yes this did not appear to occur which means there may be another explanation . . . one we don't have . . . that was his point!!

I know Mick . . . that is the point . . . to explain such a swift failure of the entire building . . . it would normally require the bottom to fail to allow the building above the foundation to fall apart supplying minimal resistance to the upper floors to fail and fall in the time we observed. And yes this did not appear to occur which means there may be another explanation . . . one we don't have . . . that was his point!!

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I thought you mean he was suggesting there was a bomb in the foundations, like lee is suggesting.

NONE of the vertical columns, whether internal or external, were capable of stably supporting their own weight. The whole structure relied on the cross-bracing of the floors, and particularly the top hat truss and the engineering floors, for stability. Without that those columns were spaghetti. Even if the column sections were 5" thick at the foundations.

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I know that. It's pretty obvious you can't have a free-standing 1000 foot tall girder. My point was more that the column would become spaghetti after just a few floors had been stripped from them, especially with a large eccentric dynamic load on them.

I thought you mean he was suggesting there was a bomb in the foundations, like lee is suggesting.

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I don't think he implicitly suggested any specific cause other than the speed of collapse wasn't supported by the official story . . . I personally don't have a specific theory . . . however, I don't think the official story fits what I witnessed . . .

I know that. It's pretty obvious you can't have a free-standing 1000 foot tall girder. My point was more that the column would become spaghetti after just a few floors had been stripped from them, especially with a large eccentric dynamic load on them.

​

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Ah. Well done with that vid! I had seen it once but was unable to rediscover it.

Bearing in mind that inverse L squared in the diagram below, then one can see the outside tower columns would be close to being compromised with TWO consecutive detached floors, even if undamaged by fire. THREE, and it would be gone with the wind.

I know that. It's pretty obvious you can't have a free-standing 1000 foot tall girder. My point was more that the column would become spaghetti after just a few floors had been stripped from them, especially with a large eccentric dynamic load on them.

​

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It is counterintuitive to me that a 110 story building could fall to the ground in ten seconds even if it were made of paper clips and tin foil. Sorry, you will have to build me a scale model to prove to me it is possible . . .

Find me a successful controlled demolition of a high-rise building of known height and known collapse time and prove to me it can be accomplished faster or in the same rate as WTC 1 . . . If WTC fell faster or the same as the demolition . . . how would you explain that??

It is counterintuitive to me that a 110 story building could fall to the ground in ten seconds even if it were made of paper clips and tin foil. Sorry, you will have to build me a scale model to prove to me it is possible . . .

Find me a successful controlled demolition of a high-rise building of known height and known collapse time and prove to me it can be accomplished faster or in the same rate as WTC 1 . . . If WTC fell faster or the same as the demolition . . . how would you explain that??

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A scale model? That's not going to help. You'd need to build a 1:1 replica.

The square cube law is one of the reasons that the "it looks weird" argument still gets traction. It does look weird. It look weird because it's so big, and our simple brains are just scaling up our experience with smaller things. But that scaling doesn't work. You can't demonstrate it with a scale model.

OK . . . High Rise steel reinforced buildings are fragile . . . until 911 no one had seen such a demonstration of fragility in the collapse of three monsters by two different mechanisms . . . in almost free fall speeds . . . so show me some similar occurrences and I might start to change my mind . . .

They are not fragile. They are very strong. The planes flew into them, and they were fine. It takes an incredible amount of force to collapse them. But once it got started, the force was unstoppable.

A rope is strong, but you can cut it with a razor blade.

I can't show you a similar occurrence, because there are no similar buildings. You are going to have to do the math.

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If the math supports it . . . show me . . . the doubters think the collapse(s) are so reminiscent of a controlled demolition you cannot tell one from the other . . . show me demolitions that collapses in less time . . . ???

3) No consideration is made for the fact that the structural aspect of the tower becomes more robust as the 'collapse' progresses. ie. more resistance the further down you go, as the lower parts of the tower are made from thicker steel, etc. eg. The vertical steels at the base of the towers were 5inches thick, 4.5foot longx2foot wide box welded columns with 3.5inch welded bracing internally. That's a beast of a thing - specially when it's tied to 46 just the same via diagonal and horizontal bracing. A beast.

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This is a point I have often raised in other debates... thanks for bringing it up here Lee, as I think it very important.

I also think it very important to note that acceleration due to gravity is only relevant when there is only the normal impedance due to air resistance and cannot be applied where further resistance is encountered.

People keep using this to demonstrate 'how it is mathematically possible for the towers to fall in such a time frame', when this really does not apply at all as the resistance of the supporting structure would significantly impede acceleration from taking place. By what factor seems impossible to conclude as there is no mathematical or evidential data on the resistance.

Long Span flooring sections are in common use and I think it important that people should be assured that the same design faults as allegedly caused wtc1, 2, & 7 to fall, are not inherent in all these other buildings.